Solution treatment of nickelchromium-cobalt alloys



United States Patent 3,333,996 SOLUTION TREATMENT OF NICKEL- CHROMIUM-COBALT ALLOYS Jack Raymond Bird, Marcus Alan Wheeler, and Geoffrey William Meetham, Derby, England, assignors to Rolls- Royce Limited, Derby, England, a company of Great Britain No Drawing. Filed June 19, 1963, Ser. No. 288,917 Claims priority, application Great Britain, July 4, 1962, 25,674/62 8 Claims. (Cl. 148-162) This invention, which is an improvement in or modification of the invention disclosed in our British specification No. 880,806, concerns the solution treatment of nickelchromium-cobalt alloys.

In British specification No. 880,806 there is disclosed an alloy having the following percentage composition by weight:

Percent Chromium l9.023 Cobalt 12.0-25 Molybdenum 3.0-8.59 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.10.5

British specification No. 880,806 suggests that the said alloy may be used in sheet form (e.g. for fabrication into gas turbine engine jet pipes and for fabrication into combustion chamber flame tubes of gas turbine engines) and to this end may be solution treated for 10 to minutes at 1060 C. to 1180 C.

High temperature furnaces for the heat treatment of very large flat sheets, which are produced in sizes up to 10 feet long by 3 feet wide, are, however, very costly to install and operate. The rate of heating of such sheets must be fast and uniform, and the sheets, or large articles made from the sheets, must be individually heat treated. For this reason, the charge loading capacity of such furnaces is low.

It is therefore of considerable economic importance to reduce, it possible, the period for which the sheets (or sheet metal articles) must be heat treated in the furnace, especially if large tonnages of thin sheet are to be solution treated. Moreover, any reduction of the said period also has the advantage of reducing oxidation penetration.

According therefore to the present invention, there is provided a method of treating an alloy having the following percentage composition by weight:

Percent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3.0-8.59

3,333,993 Patented Aug. 1, 1967 Percent Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.20.6 Silicon 0.10.5

and optionally up to 0.06% carbon, up to 1.0% iron, and up to 0.5% zirconium, the balance being nickel apart from impurities and residuals from de-oxiders, the molybdenum-titanium-aluminium factor of the alloy, as hereinbefore defined, being less than 16, said method comprising solution treating the alloy for 3 to 6 minutes at a temperature greater than 1180 C. but less than 1200 C.

The alloy which is solution treated in this way is preferably in sheet form, although it could be in the form of an extrusion or a forging.

We have found that the method of the present invention gives the alloy a more uniform grain size than that produced by solution treatment for a longer time at a lower temperature, and also gives the alloy somewhat improved strength and ductility after welding as well as appreciably improved resistance to cracking after a number of cycles of heating and cooling.

If, however, the solution treatment temperature exceeds =O C., the thermal resistance is lowered, particularly for welded sheet articles, since excessive grain growth can occur.

Preferably the alloy is solution treated at a temperature of substantially 1190 C.

After the said solution treatment, the alloy is preferably aged for substantially 8 hours at substantially 800 C., although ageing for 3 to 4 hours at 800 C. to 820 C. is adequate for many purposes.

A number of sheets of the alloy may be welded to gether to form a sheet metal article, the said ageing being carried out on the said welded sheet metal article.

The invention also comprises a sheet metal article produced by the method set forth above.

The invention is illustrated by the following example.

Example An alloy of the following percentage composition by weight was used in the fabrication of sheets having a thickness of 22 standard wire gauge:

It will be noted that the balance factor of this alloy was 15.82.

Some of the said sheets (hereinafter referred to as Sheets A) were solution treated for 10 minutes at 1150 C., were then welded together, and were aged for 16 hours at 780 C. Thus the Sheets A were not treated by the method of the present invention.

Others of the said sheets (hereinafter referred to as Sheets B) were solution treated for 3 minutes at 1190 C., were then welded together, and were aged for 8 hours at 800 C. Thus the Sheets B were treated by the method of the present invention.

The Sheets A and B were then subjected to tests at a temperature of 780 C. and the figures given in the table'below refer to the mean of three such tests.

Test Sheets A Sheets B 0.1% proof stress in tons per square inch as described in Test No. 4 of British Spec. No.

880, 800 31.0 32. Ultimate tensile strength in tons per square inch 40. 5 41. 5 Percentage elongation measured when cold on a 1.0 inch gauge length as described in Test No.2 of British specification No. 880, 806.... 8.0 9.4 Thermal cycles to failure, to 780 C., as described in Test No. l of British specification N0. 880, 806 994 3, 430 Percentage creep strain after 100 hours at 780 0. under a stress of 7.8 tons per square inch. 0.12 0.10

As will be seen from the above table, the strength and ductility after welding of the Sheets B (i.e. the sheets treated in accordance with the present invention) was slightly better than that of the Sheets A, while the Sheets B showed a markedly superior resistance to cracking under repeated treating and cooling.

The output of the high temperature furnace employed in heat treating the said sheets was moreover approximately twice as great when the Sheets B were treated therein as it was when the Sheets A were treated therein.

We claim:

II A method of treating an alloy having the following percentage composition by weight:

Percent Chromium 19.0-23 Cobalt 12.0- Molybdenum 3.0-8.59 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.10.5

Percent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3.0-8.59 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.1-0.5

and optionally up to 0.06% carbon, up to 1.0% iron, and up to 0.5% zirconium, the balance being nickel apart from impurities and residuals from de-oxidisers, the factor obtained by adding together the percentage of molybdenum, twice the percentage of aluminium and four times the percentage of titanium present in the alloy, being less than 16, said method comprising solution treating the alloy sheet for 3 to 6 minutes at a temperature of substantially 1190 C.

3. A method of treating a sheet of an alloy having the following percentage composition by weight:

Percent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3 .08.5 9 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.10.5

and optionally up to 0.06% carbon, up to 1.0% iron,

and up to 0.5% zirconium, the balance being nickel apart from impurities and residuals from de-oxidisers, the factor obtained by adding together the percentage of molybdenum, twice the percentage of aluminium and four times the percentage of titanium present in the alloy being less than 16, said method comprising solution treating the alloy sheet for 3 to 6 minutes at a temperature of substantially 1190 C. and thereafter ageing the alloy for substantially 8 hours at substantially 800 C.

4. A method of treating a sheet of an alloy having the following percentage composition by weight:

Percent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3.0-8.59 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.20.6 Silicon 0.1-0.5

and optionally up to 0.06% carbon, up to 1.0% iron, and up to 0.5% zirconium, the balance being nickel apart from impurities and residuals from de-oxidisers, the factor obtained by adding together the percentage of molybdenum, twice the percentage of aluminium and four times the percentage of titanium present in the alloy being less than 16, said method comprising solution treating the alloy sheet for 3 to 6 minutes at a temperature of substantially 1190 C. and thereafter ageing the alloy for a period of 3 to 4 hours at a temperature in the range 800 C. to 820 C.

5. A method of treating a sheet metal article formed from an alloy having the following percentage composition by weight:

Percent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3 .08.5 9 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.1-0.5

and optionally up to 0.06% carbon, up to 1.0% iron, and up to 0.5% zirconium, the balance being nickel apart from impurities and residuals from de-oxidisers, the factor obtained by adding together the percentage of molybdenum, twice the percentage of aluminium and four times the percentage of titanium present in the alloy being less than 16, said method comprising solution treating a number of sheets of the alloy for 3 to 6 minutes at a temperature greater than 1180 C. but less than 1200 C., welding the sheets together to form the sheet metal article, and ageing the sheet metal article for substantially 8 hours at substantially 800 C.

6. A method of treating a sheet metal article formed from an alloy having the following percentage composition by weight:

lPercent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3 .0-8 .59 Titanium 1.7-2.45 Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.1-0.5

and optionally up to 0.06% carbon, up to 1.0% iron, and up to 0.5 zirconium, the balance being nickel apart from impurities and residuals from de-oxidisers, the factor obtained by adding together the percentage of molybdenum, twice the percentage of aluminium and four times the percentage of titanium present in the alloy being less than 16, said method comprising solution treating a number of sheets of the alloy for 3 to 6 minutes at a temperature greater than 1180 C. but less than 1200 C.,

welding the sheets together to form the sheet metal article, and ageing the sheet metal article for a period of 3 to 4 hours at a temperature in the range of 800 C. to 820 C.

7. A method of treating a sheet metal article formed from an alloy having the following percentage composition by weight:

said method comprising solution treating a number of sheets of the alloy for 3 minutes at a temperature of substantially 1190 C., welding the sheets together to form the sheet metal article, and ageing the sheet metal article for substantially 8 hours at substantially 800 C.

8. A method of treating an alloy sheet having the following percentage composition by weight:

Percent Chromium 19.0-23 Cobalt 12.0-25 Molybdenum 3 .08.5 9

Titanium Percent Aluminium 0.3-0.74 Manganese 0.2-0.6 Silicon 0.1-0.5

and optionally up to 0.06% carbon, up to 1.0% iron and up to 0.5% zirconium, the balance being nickel apart from impurities and residuals from de-oxidisers, the factor obtained by adding together the percentage of molybdenum, twice the percentage of aluminium and four times the percentage of titanium present in the alloy being less than 16, said method comprising solution treating the alloy sheet for 3 to 6 minutes at a temperature greater than 1180 C. but less than 1200" C., and subsequently aging the alloy sheet at a temperature in the range 800 C. to 820 C.

References Cited UNITED STATES PATENTS 2,712,498 7/1955 Gresham et a1 148162 X 2,977,222 3/1961 Bieber 148--1 62 X 3,145,124 8/1964 Hig'nett et .al 148--162 3,177,075 4/ 1965 Richards et a1 148-162 X FOREIGN PATENTS 880,806 10/1961 Great Britain.

DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, Examiner.

C. N. LOVELL, Assistant Examiner. 

3. A METHOD OF TREATING A SHEET OF AN ALLOY HAVING THE FOLLOWING PERCENTAGE COMPOSITION BY WEIGHT: PERCENT CHROMIUM 19.0-23 COBALT 12.0-25 MOLYBDENUM 3.0-8.59 TITANIUM 1.7-2.45 ALUMINIUM 0.3-0.74 MANGANESE 0.2-0.6 SILICON 0.1-0.5SP@ AND OPTIONALLY UP TO 0.06% CARBON, UP TO 1.0% IRON, AND UP TO 0.5% ZIRCONIUM, THE BALANCE BEING NICKEL APART FROM IMPURITIES AND RESIDUALS FROM DE-OXIDISERS, THE FACTOR OBTAINED BY ADDING TOGETHER THE PERCENTAGE OF MOLYBDENUM, TWICE THE PERCENTAGE OF ALUMINUM AND FOUR TIMES THE PERCENTAGE OF TITANIUM PRESENT IN THE ALLOY BEING LESS THAN 16, SAID METHOD COMPRISING SOLUTION TREATING THE ALLOY SHEET FOR 3 TO 6 MINUTES AT A TEMPERATURE OF SUBSTANTIALLY 1190*C. AND THEREAFTER AGEING THE ALLOY FOR SUBSTANTIALLY 8 HOURS AT SUBSTANTIALLY 800*C. 